1. Technical Field
The present invention relates to novel catalyst components for preparing essentially amorphous copolymers of ethylene and/or alpha-olefins and, possibly, either conjugated or non-conjugated dienes. More particularly, the invention relates to the catalysts comprising such components, to the preparation of the above-mentioned copolymers using said catalysts, and to the copolymers and the vulcanized products obtained thereby.
2. Description of the Prior Art
The copolymerization of ethylene and alpha-olefins, either in the presence or in the absence of dienes, has been generally carried out with Ziegler-Natta catalysts and, in particular, with catalysts obtained by the reaction of an organometallic aluminum compound and a vanadium compound (see GB Patent Nos. 1,277,629; 1,277,353; and 1,519,472; and Italian Patent Nos. 890,604 and 879,026).
However, the activity of these catalysts and, consequently, the polymer yield relative to the amount of catalyst used, are relatively poor, especially if the diene is 1,3-butadiene. Thus, polymers obtained by these prior art methods require purification to remove catalyst residues by means of expensive supplementary processes.
Catalysts endowed with considerably higher activity for copolymerizing ethylene with alpha-olefins, which are therefore able to overcome the drawbacks described above, have been disclosed in prior patents, e.g., in U.S. Pat. Nos. 3,789,036 and 4,089,808; and Belgian Patent No. 893,443.